This invention relates to a printer device and a picture printing method. More particularly, it relates to a printer device and a picture printing device in which inks having different color hues in the color space are added in addition to conventional color inks to assure a broader color reproduction gamut.
Recently, the desk-top publishing, which is creation of documents employing a computer, is used extensively, for example, office environments. There is nowadays an increasing demand not only for letters or graphics, but also for a colored natural pictures, such as photographs, or computer graphics, which are to be output along with letters or figures. Thus it is desired to print natural pictures of high quality or computer graphics, whilst it is strongly desired to directly print the color displayed on a monitor.
In a conventional printer apparatus, employing inks of cyan of low concentration, referred to hereinafter as the low-concentration cyan, cyan of high concentration, referred to hereinafter as the high-concentration cyan, low-concentration magenta, high-concentration magenta, and of high-concentration yellow, a high-concentration ink and a low-concentration ink having the same color (color hue) are superimposed for representing the gradation. It is noted that a low-concentration yellow ink can be omitted because of its low relative luminosity factor. That is, in a conventional printer apparatus, an ink Cxe2x80x2 of the low-concentration cyan and an ink C of a high-concentration cyan are used and the amount and the ratio of emission thereof are adjusted for representing the cyan gradation. On the left side of FIG. 1, there is shown a droplet of the ink Cxe2x80x2 emitted to represent the state of the lowest gradation, whereas, on the right side of FIG. 1, there are shown four droplets of the ink Cxe2x80x2 and three droplets of the ink C emitted to represent the state of the highest gradation.
However, the above-described conventional printer apparatus has a drawback that, even if the gradation can be represented by superposition of the low-concentration ink and the high-concentration ink, the gamut of color reproduction cannot be widened due to the narrow color gamut proper to the ink. For example, in the conventional printer apparatus employing the low-concentration cyan, high-concentration cyan, low-concentration magenta, high-concentration magenta and high-concentration yellow, the gamut of color reproduction that can be represented on a monitor cannot be covered, as may be demonstrated on a L*a*b* color specification chromaticity diagram of FIG. 2, even if these inks are superimposed in combination. The result is that the conventional printer apparatus cannot meet the requirements for directly printing the colors displayed on a monitor, such that optimum results cannot be obtained on printing out high-quality natural pictures or computer graphics.
In view of the above-described status of the art, it is an object of the present invention to provide a printing apparatus and a picture printing method whereby the colors represented on a monitor can be printed clearly by broadening the gamut of color reproduction by gradation representation.
In the present invention, there is provided a printer device having four or more sorts of color inks, inclusive of high-concentration and low-concentration inks, in which at least three sorts of the inks with different color hues are used as the high-concentration inks, and one or more inks different in color hue in the color space from the above inks are used as the low-concentration inks, these inks being used for picture printing representation.
Specifically, the present invention provides a printer device for printing using at least four sorts of inks having different color hues or concentrations, wherein at least three sorts of high-concentration inks with different color hues and at least one sort of a low-concentration ink different in color hue from any of the high-concentration inks are used for printing.
Preferably, the high-concentration inks are cyan, magenta or yellow inks having different color hues from one another in the color space, or red, green and blue, similarly having different color hues from one another in the color space. The low-concentration ink used is different in color hue in the color space with respect to the aforementioned respective inks.
In the above printer device and picture printing method, the gamut for color reproduction is enhanced by increasing the number of colors of the inks in the high concentration area which is critical in determining the gamut for color reproduction. Specifically, the gradation representation and the color reproduction can be achieved for the high concentration area and the low concentration area by superimposing a high-concentration ink and a low-concentration ink in combination in picture printing representation.
According to the present invention, the colors represented on a monitor can be clearly printed out by broadening the gamut for color reproduction by gradation representation. By superimposing the high-concentration ink and the low-concentration ink in combination, the gamut for gradation representation can be broadened to enable the colors displayed on a monitor to be printed out clearly.